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UI study shows decreased risk of breast cancer in active elderly
IOWA CITY, Iowa -- Staying active may help ward off breast cancer for
postmenopausal women, according to a University of Iowa College of Medicine
study that showed the more a postmenopausal woman exercised, the less likely
she was to develop breast cancer.
"Several of us have been interested over the years in preventing
cancer," said Dr. Robert B. Wallace, professor of preventive medicine.
"The real message here is it is never too late to try to prevent a
disease such as breast cancer."
The UI findings appeared in the July issue of the Journals of Gerontology
Series A -- Biological Sciences and Medical Sciences. Prior to the UI study,
there had been only three studies evaluating physical activity during the
postmenopausal years, Wallace said. None had considered physical activity
in elderly women in the context of physical function -- whether the women
had disabilities that prevented them from being physically active.
"Unfortunately, some elderly cannot exercise because of arthritis
or other conditions," said Wallace, who noted researchers need to
identify other methods for cancer prevention among those with physical
disabilities. All older women should, of course, have periodic mammograms,
The UI study involved 1,806 women in Iowa. When the tracking started
in late 1981, none of the women had cancer. By the time the follow-ups
ended in late 1993, 46 women had developed breast cancer. Some 12 of these
women had a disability, defined as an inability to perform heavy work around
the house, walk up and down a flight of stairs or walk a half mile without
help. Of those who were physically capable of activity, 18 women described
as inactive and 14 women described as moderately active had developed breast
cancer, while only two highly active women had developed the disease.
Those with breast cancer had a higher average weight, body mass index
and systolic blood pressure.
"Obesity and lack of exercise are two sides to the same coin,"
With respect to age, height, diastolic blood pressure and menstrual
and reproductive history, there was no difference between those who had
breast cancer and those who had never had the disease. Both groups also
showed similarities in marital status, education, use of cigarettes or
alcohol and the number of times they visited their doctors in the last
While the study did not address the underlying reason for the finding,
one possible explanation might relate to insulin. Activity makes the body
more insulin sensitive, meaning the body requires less insulin to do its
job, Wallace said. Evidence has suggested that increased insulin levels
may contribute to breast cancer. Breast cancer cell cultures showed insulin
to be important in their growth and influenced the cell's movement.
The UI researchers admitted their data are limited because of the small
number of incident breast cancers and the lack of information on physical
activity during adolescence or adulthood, family history of breast cancer,
body fat distribution and diet. However, there were several strengths to
the study. The researchers relied on a population-based prospective design.
They had a high participation rate and made sure they conducted complete
follow-ups and in-person interviews. The researchers also used a cancer
registry to ascertain breast cancer diagnoses, assessed the presence of
physical disabilities, measured both recreational and home maintenance
physical activity, and controlled for many of the major known breast cancer
In addition to Wallace, the others involved in the study included these
researchers in the UI department of preventive medicine and environmental
health: principal researcher Dr. James R. Cerhan, formerly a UI assistant
professor now practicing at the Mayo Clinic; Brian C-H Chiu, a former UI
student; Jon H. Lemke, Ph.D. and UI associate professor; Dr. Charles F.
Lynch, UI professor; James C. Torner, Ph.D. and UI professor; and Linda
M. Rubenstein, a UI assistant research scientist.